Causal Loop Diagram

In many situations, causes are linear in the way that one thing cause another
thing which in turn causes something else. Causes can also go around in circles,
such a problems that seem fixed but later come back to bite you, often in
surprising ways and from unexpected directions.

The Causal Loop Diagram shows these circular actions, as below. Key variables
are shown on the diagram and these are linked with '+' to show how increasing
one variable increases the next (and decreasing the first also decreases the
second) or '-' to show that increasing one variable decreases the next (and
decreasing the first increases the second. Thus two types of loop appear:
Reinforcing loops (eg. R1), which lead to ever increasing escalation, and
balancing loops (B1), in which positive and negative changes lead to a balanced
dynamic. External constraints also act to limit any tendency to endless increase
or decrease of variables.

Examination of a causal loop diagram allows a graph of the changing variables
(a 'Behavior Over Time' Chart) to be drawn, to show the potential real-world
effects of the situation.